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[ Amazon SNS ]

send one message to many receivers

- The "event producer" only sends message to one SNS topic

- As many "event receivers(subscriptions)" as we want to listen to the SNS topic notifications

- Each subscriber to the topic will get all the messages (note: new feature to filter messages)

- Up to 10,000,000 subscriptions per topic

- 100,000 topics limit

- Subscribers can be

 1) SQS

 2) HTTP/HTTPS (with delivery retries - how many times)

 3) Lambda

 4) Emails

 5) SMS messages

 6) Mobile Notifications

1. SNS integrated with a lot of AWS services

- Many AWS services can send data directly to SNS for notifications

- CloudWatch (for alarms)

- Auto Scaling Groups notifications

- Amazon S3 (on bucket events)

- CloudFormation (upon state changes => failed to build, etc)

2. How to publish

- Topic publish (using the SDK)

 1) Create a topic

 2) Create a subscription

 3) Publish to the topic

- Direct Publish (for mobile apps SDK)

 1) Create a platform application

 2) Create a platform endpoint

 3) Publish to the platform endpoint

 4) Works with Google GCM, Apple APNS, Amazon ADM

3. Security

- Encryption :

  In-flight encryption using HTTPS API

  At-rest encryption using KMS keys

  Client-side encryption if the client wants to perform encrption/decryption inself

- Access Controls : IAM policies to regulate access to the SNS API

- SNS Access Policies (similiar to S3 bucket policies)

  Useful for cross-account access to SNS topics

  Useful for allowing other services (S3..) to write to an SNS topic

[ SNS + SQS : Fan Out(산개) ]

SNS에 메시지 푸시후 토픽을 구독중인 다수의 SQS가 메시지를 가져가는 패턴

- Push once in SNS, receive in all SQS queues that are subscribers

- Fully decoupled, no data loss

- SQS allows for : data persistence, delayed processing and retries of work

- Ability to add more SQS subscribers over time

- Make sure your SQS queue access policy allows for SNS to write

* SNS cannot send messages to SQS FIFO queues (AWS limitation)

# S3 Events to multiple queues

- For the same combination of : event type(eg: object create) and prefix (eg: images/) you can only have one S3 Event rule

- If you want to send the same S3 event to many SQS queues, use fan-out